This part of IEC 61558 deals with safety aspects of control transformers and power supplies incorporating control transformers such as electrical, thermal and mechanical safety This second edition cancels and replaces the first edition published in 1997. It constitutes a technical revision. The main changes consist of updating this Part 2-2 in accordance with Part 1, edition 2, and adding power supplies to the scope. This Part 2-2 has the status of a group safety publication in accordance with IEC Guide 104.